Help with structural failure!

[Broke dead dogg]

I've been attempting to get an interplanetary ship into kerbin orbit, and I'm having some trouble.

The initial launch goes fine, 1st staging also, but when I reach approx 23000m the kraken strikes resulting in linkage failure between the 3rd stage rhino engine and a TS-37 stack separator causing the whole upper stage to vaporise! I've tried multiple times using a combination of autostrut, regular struts, and the part rigidity on and off, with the same result. Any advise? There's no pics available unfortunately as I've been too frustrated to upload any.

(FYI, I'm on the Xbox enhanced edition, which is set to version 1.22, so no mods)

[PrvDancer85]

It could be autostrut reattaching. Do u have some autostruts on heaviest part? The heaviest part could be changing during flight due to fuel consume. I had something simular and setting autostrut to grandparent helped, maybe its the same for u. 

[bewing]

PrvDancer85's answer sounds good. Please keep in mind that landing legs automatically do a "heaviest part" autostrut. So if you have any landing legs anywhere in your craft, then you do need to pay attention to which part is heaviest.

 

[Broke dead dogg]

On 9/24/2018 at 11:15 AM, PrvDancer85 said:

It could be autostrut reattaching. Do u have some autostruts on heaviest part? The heaviest part could be changing during flight due to fuel consume. I had something simular and setting autostrut to grandparent helped, maybe its the same for u. 

Thanks I'll give it a go